Can't render an inside-out cube?
How to make backfaces transparent

For the Viewport

Enable the "Backface Culling" option. This is found in the Properties Panel under Shading > Backface Culling. The backfaces will then show as transparent in the viewport.



For Cycles Materials

Connect the Geometry node's "Backfacing" output to the "Fac" input of a Mix Shader. Then plug a Transparency Shader to the bottom input of the Mix Shader and your visible shader(s) into the top one. In this way you can factor between your visible material and transparency, or any other type of material for that matter.